Tryptophan supplementation and pH adjustment for optimizing the sporulation of <Emphasis Type="Italic">Coniothyrium minitans</Emphasis>

To determine the effect of tryptophan and pH on sporulation of Coniothyrium minitans, the fungus was cultivated using a two-stage, agar plate method in which addition of tryptophan and pH were controlled at the sporulation stage. The spore yield was enhanced by 4 times with 0.1 g tryptophan/l addition after 72 h. The optimal pH values were 4 for mycelia growth and 5.8–6 for sporulation. Mycelia grown at pH 6 had a higher productivity of spore production than did those grown at pH 4.     

Alpha-tocopheryl acetate is absorbed and hydrolyzed by Caco-2 cells comparative studies with alpha-tocopherol

Caco-2 cells were used as a model for investigating and comparing the absorption of alpha-tocopherol (Tol) and alpha-tocopheryl acetate (Tac) solubilized in micelles based on a mixture of sodium taurocholate (NaTC) and oleic acid. Surprisingly, the uptake of Tac was found to be similar to that of Tol, and in both cases, the dose-response plots suggest that protein-mediated transport processes were involved. Moreover Tol or Tac were also secreted into the basolateral medium of Caco-2 cells but Tac was mainly hydrolyzed either prior to absorption or intracellularly. The solubilization of Tol or Tac by NaTC on the apical side of the cell monolayer is a prerequisite for the uptake process, although larger amounts of the bile salt are necessary to solubilize Tac than Tol. Caco-2 cells showed hydrolytic activity on Tac, and additional cholesterol esterase may be taken up by the cells, thus increasing the rates of intracellular hydrolysis of Tac. Based on our findings, a scheme is suggested accounting for the absorption of alpha-tocopheryl acetate by enterocytes.     

Statins activate a mitochondria-operated pathway of apoptosis in breast tumor cells by a mechanism regulated by ErbB2 and dependent on the prenylation of proteins

Statins are inhibitors of the mevalonate synthesis pathway that induce apoptosis in tumor cells although the apoptotic mechanism activated by statins remains to be elucidated. We have examined the role of the mitochondria-operated pathway of apoptosis in the cell death induced by statins in breast tumor cells and its regulation by protein prenylation and ErbB2 overexpression. Lovastatin treatment down-regulates the expression of Bcl-2 and activates apoptosis through a mitochondria-operated, ErbB2- regulated mechanism. Apoptosis induced by statins is independent of their effects on cholesterol synthesis and involves protein prenylation. Our results indicate that prenylation of apoptosis-regulating proteins is a key event in the survival of breast tumor cells and this requirement could be circumvented in cells overexpressing the oncogene ErbB2.     

Growth inhibition of the eight species of microalgae by growth inhibitor from the culture of Isochrysis galbana and its isolation and identification

A type of growth inhibitor was successfully isolated and purified from cell-free filtrates of cultural medium at the death phase of Isochrysis galbana, and its chemical structure was confirmed by the methods of FABMS, UV, ¹H-NMR, ¹³C-NMR and 2D NMR, which was 1-[hydroxyl-diethyl malonate]-isopropyl dodecenoic acid, C₂₂H₃₈O₇. The results showed that the growth-inhibitor strongly inhibited the growth of Isochrysis galbana, and the growth of the eight species of microalgae (Dunaliella salina, Platymonas elliptica, Chlorella vugralis, Nitzschia closterium, Chaetoceros muelleri, Chaetoceros gracilis, Nitzschia closterium minutissima, Phaeodactylum tricornutum) also could be regulated by the growth-inhibitor in a concentration-dependent manner. The further investigation found that the synthesis process of chlorophyll and protein in the cells of all test microalgae could be inhibited by the growth inhibitor, and the content of chlorophyll and protein significantly decreased.     

Effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater

The effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater was investigated. Experiments were conducted in a modified Ludzack–Ettinger pilot-plant configuration for 365 days. Total nitrification of an influent concentration of 1200 mg NH₄⁺–N l⁻¹ was obtained in this period. Influent COD/N ratios between 0.71 and 3.4 g COD g N⁻¹ were tested by varying the nitrogen loading rate (NLR) supplied to the pilot plant. An exponential decrease of nitrification rate was observed when the influent COD/N ratio increased.

The experimental COD/N ratio for denitrification was 7.1±0.8 g COD g N⁻¹ while the stoichiometric ratio was 4.2 g COD g N⁻¹. This difference is attributable to the oxidation of organic matter in the anoxic reactor with the oxygen of the internal recycle. The influence of influent COD/N ratio on the treatment of high-strength ammonium industrial wastewater can be quantified with these results. The influence of COD/N ratio should be one of the main parameters in the design of biological nitrogen removal processes in industrial wastewater treatment.     

The Importance of Molecular Parameters of Quaternary Ammonium Salts in Their Antigibberellin (Retardant) Activity

The importance of six theoretically calculated molecular parameters in the antigibberellin (retardant) activity of quaternary ammonium salts is studied using a regression analysis. A bioassay system based on cell culture of fungus Gibberella fujikuroi is used to determine the activity. In the case of N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium chloride (choline) and N,N,N-triethyl-N-(2-hydroxyethyl)ammonium chloride (N,N,N-triethylcholine) derivatives with linear structure, the polarizability, proton acceptor activity, and lipophilicity of these compounds exert the largest effect on the antigibberellin activity. The antigibberellin activity of more sterically hindered N,N-dialkylpiperidinium salts was mainly defined by the steric parameter, while the polarizability, proton acceptor activity, and (through them) lipophilicity exert a lesser effect. Other parameters are of minor importance for the three groups of compounds studied.     

Lipase-catalyzed ammonolysis of trimethylsilylmethyl acetate in organic solvent

Lipase could catalyze the ammonolysis of trimethylsilylmethyl acetate in organic solvents and Novozym 435 was the best biocatalyst for the reaction. The influences of some factors on the reaction were investigated. Cyclohexane, n-hexane and heptane were found to be suitable reaction media and ammonium carbamate was the best ammonium source. The optimal initial water activity, temperature and pH value were 0.55-0.75, 35°C and 6.5 respectively, under which a substrate conversion of 97.6% could be achieved after reaction for 140 h.     

Determination of rat serum esterase activities by an HPLC method using S-acetylthiocholine iodide and p-nitrophenyl acetate

Establishing esterase assays allows the determination and comparison of esteratic activities of tissues of one organism and between organisms. We have developed a high-performance liquid chromatography (HPLC) assay for the determination of S-acetylthiocholine (ATC) and p-nitrophenyl acetate (NPA) hydrolyzing activities of rat serum esterases based on ion pair chromatography with on-line radiochemical and ultraviolet (UV) detection. ATC is a substrate for cholinesterases, whereas NPA is cleaved by a variety of esterases and other proteins (e.g., cholinesterases, paraoxonase, carboxylesterase, albumin). Both substrates were incubated, simultaneously or separately, with rat serum to explore potential interferences between the enzymatic hydrolyses of the compounds. The ratio of the peak area of the ¹⁴C-labeled substrates to the total peak area of the substrates and their corresponding cleavage products was compared with the UV quantitation of ATC and p-nitrophenolate (NP), the cleavage product of NPA, measured at 230 and 350 nm, respectively. The peak identity of ATC and NP was confirmed by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). The reaction rates of the assays using one substrate or both, as well as using radiochemical or UV detection, were equal. Moreover, the correlation between rat serum volumes and reaction rates was shown for both substrates. In conclusion, one can (i) choose between the two detection methods reliably, (ii) take advantage of monitoring both substrate and product by using radiochemical detection, and (iii) combine both substrates to determine esterase activities in rat serum and probably other biological matrices.     

Spontaneous formation of DPPC monolayers at aqueous/vapor interfaces and the impact of charged surfactants

Surface tensiometry and vibrational sum-frequency spectroscopy were used to examine the structure and organization in phospholipid monolayers at the aqueous/vapor interface in the absence and in the presence of simple, charged surfactants. 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was the phospholipid employed in these studies and surfactants included sodium dodecyl sulfate (SDS) and dodecyl trimethyl ammonium bromide (DTAB). DPPC spontaneously spreads on a pure water (pH = 5.5) surface to form monolayers as evidenced by an equilibrium spreading pressure (ESP) of 7.9 ± 2.3 mN/m and a clearly resolved vibrational spectrum. Low concentrations of surfactants inhibit the spreading of DPPC and result in significantly lower ESP values. Anionic and cationic surfactants at higher concentrations have opposite effects on monolayer organization; SDS creates well-organized monolayers while DTAB leads to poor organization of lipid molecules. Surface-specific vibrational spectra showed that high concentrations of charged surfactants (≥ 100 µM) lead to accumulation of net surface charges as evidenced by destructive and constructive interferences. Selectively deuterating surfactants results in changes in vibrational band intensities and phases enabling assignment of relative orientations of equivalent functional groups belonging to the lipid and surfactant.